The sequence listing that is contained in the file named “GENUP0032US_ST25.txt”, which is 40 KB (as measured in Microsoft Windows®) and was created on Jul. 25, 2016, is filed herewith by electronic submission and is incorporated by reference herein.
1. Field of the Invention
The present invention relates generally to the fields of medicine, oncology and immunotherapeutics. More particularly, it concerns the development of immunoreagents for use in detecting and treating MUC1-positive cancers.
2. Background of the Invention
Mucins are extensively O-glycosylated proteins that are predominantly expressed by epithelial cells. The secreted and membrane-bound mucins form a physical barrier that protects the apical borders of epithelial cells from damage induced by toxins, microorganisms and other forms of stress that occur at the interface with the external environment. The transmembrane mucin 1 (MUC1) can also signal to the interior of the cell through its cytoplasmic domain. MUC1 has no sequence similarity with other membrane-bound mucins, except for the presence of a sea urchin sperm protein-enterokinase-agrin (SEA) domain (Duraisamy et al., 2006). In that regard, MUC1 is translated as a single polypeptide and then undergoes autocleavage at the SEA domain Macao, 2006).
MUC1 has been studied extensively by the inventors and others for its role in cancer. As discussed above, human MUC1 is heterodimeric glycoprotein, translated as a single polypeptide and cleaved into N- and C-terminal subunits (MUC1-N and MUC1-C) in the endoplasmic reticulum (Ligtenberg et al., 1992; Macao et al., 2006; Levitin et al., 2005). Aberrant overexpression of MUC1, as found in most human carcinomas (Kufe et al., 1984), confers anchorage-independent growth and tumorigenicity (Li et al., 2003a; Huang et al., 2003; Schroeder et al., 2004; Huang et al., 2005). Other studies have demonstrated that overexpression of MUC1 confers resistance to apoptosis induced by oxidative stress and genotoxic anti-cancer agents (Yin and Kufe, 2003; Ren et al., 2004; Raina et al., 2004; Yin et al., 2004; Raina et al., 2006; Yin et al., 2007).
The family of tethered and secreted mucins functions in providing a protective barrier of the epithelial cell surface. With damage to the epithelial layer, the tight junctions between neighboring cells are disrupted, and polarity is lost as the cells initiate a heregulin-induced repair program (Vermeer et al., 2003). MUC1-N is shed from the cell surface (Abe and Kufe, 1989), leaving MUC1-C to function as a transducer of environmental stress signals to the interior of the cell. In this regard, MUC1-C forms cell surface complexes with members of the ErbB receptor family, and MUC1-C is targeted to the nucleus in the response to heregulin stimulation (Li et al., 2001; Li et al., 2003c). MUC1-C also functions in integrating the ErbB receptor and Wnt signaling pathways through direct interactions between the MUC1 cytoplasmic domain (CD) and members of the catenin family (Huang et al., 2005; Li et al., 2003c; Yamamoto et al., 1997; Li et al., 1998; Li et al., 2001; Li and Kufe, 2001). Other studies have demonstrated that MUC1-CD is phosphorylated by glycogen synthase kinase 3β, c-Src, protein kinase Cδ, and c-Abl (Raina et al., 2006; Li et al., 1998; Li et al., 2001; Ren et al., 2002). Inhibiting any of the foregoing interactions represents a potential point of therapeutic intervention for MUC1-related cancers.